Microlens arrays are used in applications where gathering light from a source and then directing it to various locations and in various angles is desirable. Such applications include computer displays, screens for projection televisions, and certain illumination devices. The utility of the array can often be enhanced by inclusion of an aperture mask which only permits light to pass through the array in certain directions and which absorbs ambient light which would otherwise reflect off of the surface of the array and degrade the effective contrast of the optical system. Such arrays and masks with apertures may be conventionally formed at the points at which the lenses focus paraxial radiation.
Conventional techniques for creating microlens arrays with aperture masks may involve fabrication of the arrays on suitable substrates which are or can be coated with appropriate radiation absorbing mask materials. High intensity radiation is then directed through the lenses and focused by them. If the structure of the lens array, substrate and mask has been designed so that the focal points of the lens array are at or near the mask layer, the radiation will form apertures in the mask at these focal points. See, for example, U.S. Pat. No. 4,172,219 to Deml et al., entitled Daylight Projection Screen and Method and Apparatus for Making the Same.
Microstructure arrays in optically transparent materials are used in applications where gathering light from a source and then directing it to various locations and in various angles may be desirable. When coated with reflective materials, such arrays can function as retroreflectors, reflecting light from a source back in the direction from which it entered the material.
Retroreflective materials have found a wide range of applications, particularly in signage and advertising in which clear visibility is desirable when illuminated at night. Additional applications include front projection screens. In many of these applications of retroreflective materials, for example road signs and markings, ease of manufacture and low cost may be desirable. The materials should also be easy to apply, weather-resistant and/or durable.
Particles of sizes ranging from about 10 microns-250 microns may be widely used in a range of chemical, biochemical, and/or pharmaceutical activities. For example, micron-sized spherical beads are used whose surfaces can provide sites for chemical reactions. Catalysis of chemical reactions can be promoted and controlled in this manner. Pharmaceutical delivery platforms can also be produced in this way.
The utility of these particles may depend on their availability in a monodispersed form. In monodispersed particles, the sizes of the particles should be accurately controlled so that, in turn, the surface area available for the reaction site is accurately known. Producing particles of a tightly controlled size and then sieving them to produce monodispersed collections may be time consuming and/or expensive.
Current techniques for forming micron sized particles from polymeric materials involve spraying or otherwise forcing the material in liquid form through a nozzle to form a stream and then breaking up this stream into particles using a variety of methods. Current methods for sieving the particles to obtain accurately monodispersed collections may be time consuming.
Certain types of displays, such as Liquid Crystal Displays (LCD) often use backlighting to achieve contrast and brightness levels for comfortable viewing. In applications such as laptop computers it may also be desirable to reduce overall power consumption.
Typically laptop computer displays are illuminated by small thin fluorescent tubes. The light from these tubes enters a wedge shaped piece of transparent plastic with reflective inclusions on its rear side, which acts as a light guide. Light which strikes the reflective inclusions bounces in various directions, some of it forward to the screen, some of it backward to a reflector behind the light guide, and bounces from there forward towards the screen and the remainder of the light goes in various other directions. Since the brightness of the fluorescent tube may be limited to reduce power consumption, the light that is not directed in useful directions should somehow be redirected towards the screen. Conventionally, light management films are placed between the light guide and the liquid crystal panel, which act to transmit light which is heading towards the panel and to reflect light which is traveling in other directions back towards the rear of the display stack. This light is then scattered by the reflective inclusions in the light guide and the transmission and reflection begin again, a type of “recycling” of light. Light which emerges from this light management film is directed towards the liquid crystal panel and emerges from the display at angles which are desirable for normal viewing.
The films that are conventionally used for such light management purposes are composed of films containing prismatic structures and which permit light incident on the films at certain angles to pass through while the remaining light is reflected by total internal reflection (TIR). The nature of the use of the films is such that it is generally desirable for the structures to be formed without seams or other joins or features which may interfere with the quality of the visible image.
Articles which contain large numbers of small shapes or structures are used in many applications from television and computer displays to microfluidics. For purposes of mass manufacturing, the small shapes or structures in these articles are conventionally produced first in a single “master” and then reproduced or replicated onto a “stamper” which contains negative images of the shapes on the master. The stamper can then be employed as a “tool” in web-to-web or similar replication process to reproduce the shapes on the original master over and over again. The quality of shapes or structures in each of the replicas may depend in large measure on the quality of the master and the stamper so that it is desirable for each stage in its production be carried out with precision.
Replication of the shapes on the master may involve embossing or otherwise pressing the master and the shapes thereon into a softer material. Once this material has hardened the master and the copy of it that have been made (the stamper) should be separated without damaging either. A similar process is carried out to make copies of the stamper. Conventionally, the stamper is pre-treated with some form of release agent to promote separation. Often this involves depositing a thin film of relatively inert inorganic or organic material onto the stamper prior to its use as a replication tool. In the replication of large stampers, this can be a difficult and time consuming process while errors in this process can significantly degrade overall production yields. Hence, it may be desirable to have masters which do not need to use such pre-treatment.
High powered Infrared (IR) Lasers can be particularly difficult and dangerous to use since the radiation beam is not visible. Apart from expensive and cumbersome solutions such as IR goggles, conventionally a material known as “burn paper” is used to identify the beam location. This paper, when exposed to the beam, will display a burned area or spot. Examination of the spot often reveals some level of detail about the spatial profile of the beam. Since it is not desirable that smoke or particles from the burn enter the atmosphere around the laser, potentially degrading optical components, the paper is normally held in a sealed plastic bag. It is desirable to have a more effective tool for locating IR laser beams and providing basic information regarding their spatial profile.
The image quality of many display devices can be degraded by the effects of ambient light reflecting from the display surface and interfering with the display image. In extreme cases, for example when viewing a computer display in daylight conditions, ambient light may completely “wash out” the image, rendering it unviewable. Anti-reflection coatings are available in certain instances, but these may be costly, may be difficult to apply to materials such as plastics, and/or may themselves interfere with image quality.
A second problem which may adversely affect the performance of displays is the inability to distribute the available light emerging from the display to the various points or spatial positions at which viewers may wish to use or view the display. Since it often desirable to conserve available light, designers may attempt to concentrate the intensity of the light emerging from the screen into areas where viewers are most likely to be found. The ability of a screen to so concentrate light is referred to as its gain. In applications such as televisions, the viewing area generally is not isotropically distributed with respect to the screen. Viewers are much more likely to be distributed at relatively high angles from the normal in the horizontal axis, while being distributed at much lower angles from the normal in the vertical axis. Diffusers which are isotropic thus, in effect, may waste a great deal of illumination by throwing it into positions where viewers are more unlikely to be found.
A third problem which may adversely affect screen performance is the presence of artifacts such as moiré patterns or other instances of aliasing, as well as speckle and related artifacts related to coherence phenomena. These problems, although subtle, may be pervasive and may account for an overall perception that images produced by a display lack clarity or sharpness.